Blood Pressure Measurement Methods Research Articles

A feature exploration methodology for learning based cuffless blood pressure measurement using photoplethysmography.

In this work, we propose a feature exploration method for learning-based cuffless blood pressure measurement. More specifically, to efficiently explore a large feature space from the photoplethysmography signal, we have applied several analytical techniques, including random error elimination, adaptive outlier removal, maximum information coefficient and Pearson's correlation coefficient based feature assessment methods. We evaluate fifty-seven possible feature candidates and propose three separate feature sets with each containing eleven features to predict the systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean blood pressure (MBP), respectively. From our experimental results on a realistic dataset, this work achieves 4.77±7.68, 3.67±5.69 and 3.85±5.87 mmHg prediction accuracy for SBP, DBP and MBP. In summary, using the proposed light-weight features, the proposed predictors can successfully achieve a Grade A in two standards proposed by the American National Standards of the Association for the Advancement of Medical Instrumentation (AAMI) and British Hypertension Society (BHS).

Effect of Olanzapine on Mean Arterial Blood Pressure: An Experimental Study

Introduction: Schizophrenia or psychosis, a major group of CNS disorders which results in serious distortion of one’s capacity to recognize reality, affects approximately 1 % of world population. Olanzapine is an atypical antipsychotic which is efficacious in the treatment of schizophrenia. Orthostatic hypotension is commonly reported as compared to hypotension itself. Thus we propose this study to evaluate hypotensive effect of olanzapine and to delineate its probable mechanism. Materials and methods: Adult albino wistar rats (200–250mg) of either sex were grouped into six groups each containing six animals. Groups 1 received 10ml/kg normal saline, groups 2, 3, 4 received olanzapine (0.5, 1.5, 5mg/kg respectively), groups 5, 6 received prazosin (0.5, 1.5mg/kg respectively) intraperitoneally and blood pressure was measured after 0, 30, 60 &120 minute by using non invasive blood pressure (NIBP) measurement method . Results: Administration of low dose of olanzapine caused no significant change in blood pressure but in higher doses (1.5, 5 mg/ kg) there was significant fall in BP. These effects were similar to prazosin 0.5 & 1.5mg/kg. Conclusion: Olanzapine in human dose equivalent (1.5 & 5mg/kg) produces significant fall in BP in rats, which

Dual-modality arterial pulse monitoring system for continuous blood pressure measurement.

Accurate and ambulatory measurement of blood pressure (BP) is essential for efficient diagnosis, management and prevention of cardiovascular diseases (CVDs). However, traditional cuff-based BP measurement methods provide only intermittent BP readings and can cause discomfort with the occlusive cuff. Although pulse transit time (PTT) method is promising for cuffless and continuous BP measurement, its pervasive use is restricted by its limited accuracy and requirement of placing sensors on multiple body sites. To tackle these issues, we propose a novel dual-modality arterial pulse monitoring system for continuous blood pressure measurement, which simultaneously records the pressure and photoplethysmography (PPG) signals of radial artery. The obtained signals can be used to generate a pressure-volume curve, from which the elasticity index (EI) and viscosity index (VI) can be extracted. Experiments were carried out among 7 healthy subjects with their PPG, ECG, arterial pressure wave and reference BP collected to examine the effectiveness of the proposed indexes. The results of this study demonstrate that a linear regression model combining EI and VI has significantly higher BP tracking correlation coefficient as compared to the PTT method. This suggests that the proposed system and method can potentially be used for convenient and continuous blood pressure estimation with higher accuracy.

A new estimate technology of non-invasive continuous blood pressure measurement based on electrocardiograph

Various physiological parameters have been widely used in the prevention and detection of diseases. In particular, the occurrence of cardiovascular diseases can be observed through daily measurement of blood pressure. Currently, the most common blood pressure measurement method records blood pressure on the upper arm. This can lead to the subject feeling uncomfortable and tension in the arm from the stress may lead to measurement errors. An electrocardiogram represents the electrical activity during heart function, but also contains blood pressure–related information. This study is an attempt to extract features related to blood pressure from the electrocardiogram signal using a new non-invasive blood pressure measurement technology that utilizes intelligent neural network algorithms to calculate blood pressure values from electrocardiogram parameters. In this study, the average error rate of the blood pressure measurement was lower than 5% compared to the common blood pressure machine. The proposed approach alleviates the errors caused by discomfort, which provides a more feasible method to continuously monitor blood pressure in less stressful conditions. This technology has significant potential for advancing healthcare.

Patient preferences for different methods of blood pressure measurement: is ethnicity relevant?

Patient preferences for different methods of blood pressure measurement: is ethnicity relevant?

0270 : Ambulatory blood pressure monitors in our daily practice: why use it more often?

Discordance between blood pressure (BP) measurement methods can occur and create ambiguity. The automated BP monitors (ABPM) are already available for years, In addition to 24-hour values, the circadian variation of BP adds prognostic significance in predicting cardiovascular outcome. But this devises are no often prescribed in our population. The objective of this study is to quantify concordance among BP measurement methods and to define the diagnostic sensitivity, specificity, and prognostic value of ABPM in a Moroccan population of hypertensive patients. The office mercury sphygmomanometer, the ambulatory BP monitor (ABPM), with an oscillometric device, and home self-measurement with an automatic device were compared in an observational prospective study. 50 patients were enrolled. Ambulatory BP monitoring was performed. A nondipping pattern was defined when nocturnal systolic BP dip was < 10% of daytime systolic BP Average BP results were similar between measurement methods with the exception of daytime ABPM, which was significantly higher: sphygmomanometer, 127.9±12.3/83.9±7.3 mm Hg; 24-hour ABPM, 132.6±10.7/ 84,2±8.7 mm Hg; day ABPM, 136.5±12.5/86.0±11.9 mm Hg; home self-measurement, 131.0±14.3/82.5±8.2 mm Hg. Discordance in the achievement of therapeutic goals was observed in 23 patients, with only 6 cases being explained by masked hypertension or “white coat syndrome” according to all measurements. The prevalence of nondipping was 44%, the nondipping pattern was associated with advanced age, obesity, diabetes, and overt cardiovascular or renal disease. the 3 measurement strategies provide similar average BP estimates. The ABPM device can be very valuable to rise some ambiguity and can give important prognostic information. The author hereby declares no conflict of interest

Blood Pressure Measurement Biases in Clinical Settings, Alabama, 2010-2011.

IntroductionBlood pressure measurement in clinical care settings seldom follows the protocol recommended by national guidelines, potentially leading to overestimates or underestimates of blood pressure control. We evaluated blood pressure measurement methods as a source of bias in determining blood pressure control among community-dwelling adults with diabetes.MethodsIn a community-based trial of patients with diabetes, we measured both “clinical blood pressure” (clinical BP) (taken by a community nurse or medical assistant instructed to “take the participant’s blood pressure like you do in your own clinic”) and “research blood pressure” (research BP) (research staff followed a guideline-concordant protocol). Each participant had both types of blood pressure assessment on the same day over the course of 2 hours.ResultsThe 227 participants had a mean age of 59 years; 86% were black and 74% were women. The mean clinical BP was 5 mm Hg higher than the mean research BP for systolic blood pressure (P < .001) and 2 mm Hg higher for diastolic blood pressure (P < .001). The proportion of participants whose clinical BP was 130/80 mm Hg or higher was 8 percentage points higher than the proportion whose research BP was 130/80 mm Hg or higher (P < .001), and the proportion whose clinical BP was 140/90 mm Hg or higher was 10 percentage points higher than the proportion whose research BP was 140/90 mm Hg or higher (P < .001). Among those aged 65 years or older, the proportion whose clinical BP was 130/80 mm Hg or higher was 10 percentage points higher than proportion whose research BP was 130/80 mm Hg or higher, and the proportion whose clinical BP was 140/90 mm Hg or higher was 14 percentage points higher than the proportion whose research BP was 140/90 mm Hg or higher. Whites and smokers had the greatest risk for having a clinical BP 5 mm Hg or more higher than their research BP.ConclusionMeasurement biases in clinical settings may be a component of observed poor blood pressure control rates in real-world settings.

Agreement between ambulatory, home, and office blood pressure variability.

Ambulatory, home, and office blood pressure (BP) variability are often treated as a single entity. Our aim was to assess the agreement between these three methods for measuring BP variability. Twenty-four-hour ambulatory BP monitoring, 28 home BP measurements, and eight office BP measurements were performed on 461 population-based or hypertensive participants. Five variability indices were calculated for all measurement methods: SD, coefficient of variation, maximum-minimum difference, variability independent of the mean, and average real variability. Pearson's correlation coefficients were calculated for indices measured with different methods. The agreement between different measurement methods on the diagnoses of extreme BP variability (participants in the highest decile of variability) was assessed with kappa (κ) coefficients. SBP/DBP variability was greater in daytime (coefficient of variation: 9.8 ± 2.9/11.9 ± 3.6) and night-time ambulatory measurements (coefficient of variation: 8.6 ± 3.4/12.1 ± 4.5) than in home (coefficient of variation: 4.4 ± 1.8/4.7 ± 1.9) and office (coefficient of variation: 4.6 ± 2.4/5.2 ± 2.6) measurements (P < 0.001/0.001 for all). Pearson's correlation coefficients for systolic/diastolic daytime or night-time ambulatory-home, ambulatory-office, and home-office variability indices ranged between 0.07-0.25/0.12-0.23, 0.13-0.26/0.03-0.22 and 0.13-0.24/0.10-0.19, respectively, indicating, at most, a weak positive (r < 0.3) relationship. The agreement between measurement methods on diagnoses of extreme SBP/DBP variability was only slight (κ < 0.2), with the κ coefficients for daytime and night-time ambulatory-home, ambulatory-office, and home-office agreement varying between-0.014-0.20/0.061-0.15, 0.037-0.18/0.082-0.15, and 0.082-0.13/0.045-0.15, respectively. Shorter-term and longer-term BP variability assessed by different methods of BP measurement seem to correlate only weakly with each other. Our study suggests that BP variability measured by different methods and timeframes may reflect different phenomena, not a single entity.

Understanding Blood Pressure Variation and Variability: Biological Importance and Clinical Significance.

Variability is a normative property of blood pressure necessary for survival which likely contributes to morbidity and mortality through allostatic load. Because of its allostatic and adaptive properties blood pressure responses to peculiar situations like the visit to the clinic can lead to the misdiagnosis of hypertension. Cuff methods of blood pressure measurement can also create blood pressure variation when there really is none. There are also physiological differences between populations related to their evolutionary history that likely further affect the extent of population differences in 24-h blood pressure variability. Quantifying the sources and extent of blood pressure variability can be done using natural experimental models and through the evaluation of ecological momentary data. It is very likely that the results of population studies of blood pressure variability and morbidity and mortality risk are inconclusive because the parameters used to assess blood pressure variability do not reflect the actual nature of blood pressure allostasis.

Effect of Cuff Placement on Blood Pressure Measurement in Conscious Healthy Dogs

Blood pressure determination is a very helpful aid in the diagnosis and monitoring of several diseases in small animal medicine. Non-invasive methods for blood pressure measurement are currently the most rapid and practical alternative in the clinical setting, however only few studies have dealt with selecting the best cuff position for its determination. The aim of the study was to determine the best site for cuff placement (limbs and tail) during noninvasive blood pressure in healthy subjects. Arterial blood pressure was measured by use of an oscilometric system in 22 clinically healthy dogs. Five consecutive measurements were obtained from five different sites: left and right median arteries, left and right tibial cranial arteries and coccygeal artery then were compared. Significant differences were found in systolic blood pressure measured from the right hind limb. Heart rate, age, and weight were not found to have a significant influence on arterial blood pressure. We suspect that the long duration of the procedure was the culprit, leading to stress, which as a result, led to higher blood pressure on the mentioned limb. Based on our results, we concluded that all limbs as well as the tail are suitable sites for routine blood pressure determination, as long as the procedure is completed within a rational time period.

Blood pressure measurement in hemodialysis: The importance of the measurement technique.

Systemic arterial hypertension contributes to the high cardiovascular morbidity in hemodialysis (HD) patients, but the accuracy of blood pressure (BP) measurement in this population has not been well studied. To evaluate the agreement between BP measurement using the routine measurement technique (usual method) and the technique recommended by the VII Joint (standard method). This cross-sectional study enrolled 124 patients in a single center who had undergone dialysis for more than three months and were 18 years of age or older. The BP was verified at the start of dialysis by the nursing team (usual method) and by the researchers (standard method). The agreement between the systolic and diastolic BP (SBP and DBP) measurements was tested by the Bland-Altman analysis. A difference in BP measurement higher than ±5 mm Hg was considered clinically significant. The studied group had a mean age of 53.2 years. The average difference between routine and standard BP measurement was -6 mm Hg for SBP (limits of agreement: -40.1-28 mm Hg; P <0.001) and -5.6 mm Hg for DBP (limits of agreement: -33.1-21.8 mm Hg; P <0.001). A clinically significant difference in BP measured by both methods was observed in 69.4% of the patients for SBP and in 61.3% for DBP. The disagreement between the results of different BP measurement methods in HD patients was significant and the BP was underestimated using the usual BP method. BP measurement standardization should be encouraged to avoid errors in diagnosis and therapy.

Patient-Specific Oscillometric Blood Pressure Measurement.

Most automatic cuff blood pressure (BP) measurement devices are based on oscillometry. These devices estimate BP from the envelopes of the cuff pressure oscillations using fixed ratios. The values of the fixed ratios represent population averages, so the devices may only be accurate in subjects with normal BP levels. The objective was to develop and demonstrate the validity of a patient-specific oscillometric BP measurement method. The idea of the developed method was to represent the cuff pressure oscillation envelopes with a physiologic model, and then estimate the patient-specific parameters of the model, which includes BP levels, by optimally fitting it to the envelopes. The method was investigated against gold standard reference BP measurements from 57 patients with widely varying pulse pressures. A portion of the data was used to optimize the patient-specific method and a fixed-ratio method, while the remaining data were used to test these methods and a current office device. The patient-specific method yielded BP root-mean-square-errors ranging from 6.0 to 9.3 mmHg. On an average, these errors were nearly 40% lower than the errors of each existing method. The patient-specific method may improve automatic cuff BP measurement accuracy. A patient-specific oscillometric BP measurement method was proposed and shown to be more accurate than the conventional method and a current device.

DIASTOLIC BLOOD PRESSURE OR ACTUALLY IT IS BASELINE SYSTOLIC BLOOD PRESSURE?

Blood pressure measuring represents a routine investigation in general medicine. Nokolai Korotkoff was only 31 years old when he made a short presentation to the Scientific Meeting of the Military Hospital of the Academy on 5 November 1905 concerning an easy non-invasive method of blood pressure (BP) measurement, entitled ‘Concerning the problems of the methods of blood pressure measurement’. If the pressure in the cuff is relieved, blood starts coming through the compressed arterial segment during systole and causes auscultatory sound and, the first sound, which, in Korotkoff’s opinion, is a measurement of systolic blood pressure. In the same BP measurement, when normal blood flow is fully restored, the auscultatory sounds disappear and, the last sound, which, in Korotkoff’s opinion is a measurement of diastolic blood pressure. Listening to Korotkoff sounds (K-sounds) to determine systolic and diastolic blood pressure (BP) has been the standard for noninvasive BP measurement in medical practices for nearly 100 years and it is the essential tool used for evaluation and assessment of patients with hypertension and risks of cardiovascular diseases (CVD) by physicians and nurses despite limited understanding of the nature of K-sounds. This article focuses particularly on the cardiovascular biomechanics of the first and last auscultatory sound and suggests two new terminologies; Highest systolic blood pressure and Baseline systolic blood pressure to represent the systolic pressure and diastolic pressure, respectively. Experimenting blood pressures on the basis of these two new suggested terminologies may reveal various additional undiscovered aspects of normal BP and abnormal BP.

Photoplethysmogram intensity ratio: A potential indicator for improving the accuracy of PTT-based cuffless blood pressure estimation.

The most commonly used method for cuffless blood pressure (BP) measurement is using pulse transit time (PTT), which is based on Moens-Korteweg (M-K) equation underlying the assumption that arterial geometries such as the arterial diameter keep unchanged. However, the arterial diameter is dynamic which varies over the cardiac cycle, and it is regulated through the contraction or relaxation of the vascular smooth muscle innervated primarily by the sympathetic nervous system. This may be one of the main reasons that impair the BP estimation accuracy. In this paper, we propose a novel indicator, the photoplethysmogram (PPG) intensity ratio (PIR), to evaluate the arterial diameter change. The deep breathing (DB) maneuver and Valsalva maneuver (VM) were performed on five healthy subjects for assessing parasympathetic and sympathetic nervous activities, respectively. Heart rate (HR), PTT, PIR and BP were measured from the simultaneously recorded electrocardiogram (ECG), PPG, and continuous BP. It was found that PIR increased significantly from inspiration to expiration during DB, whilst BP dipped correspondingly. Nevertheless, PIR changed positively with BP during VM. In addition, the spectral analysis revealed that the dominant frequency component of PIR, HR and SBP, shifted significantly from high frequency (HF) to low frequency (LF), but not obvious in that of PTT. These results demonstrated that PIR can be potentially used to evaluate the smooth muscle tone which modulates arterial BP in the LF range. The PTT-based BP measurement that take into account the PIR could therefore improve its estimation accuracy.

Blood pressure monitoring during exercise: Comparison of pulse transit time and volume clamp methods

During physical exercise, pulse transit time (PTT), expressed as the interval between ventricular electrical activity and peripheral pulse wave, may provide a surrogate estimate for blood pressure by the use of specific calibration procedures. The objective of this study was to determine systolic blood pressure (SBP) values derived from the PTT method and from an established method of non-invasive continuous blood pressure measurement based on the volume clamp technique, and to compare their agreement with sphygmomanometry during exercise tests. In 18 subjects, electrocardiogram (ECG) and finger-photoplethysmography were continuously recorded during maximal cycle exercise tests. Intermittent and continuous blood pressure measurements were simultaneously taken using automated sphygmomanometry and a Portapres Model-2 device, respectively. PTT was calculated for each ECG R-wave and the corresponding steepest upstroke slope in the photoplethysmogram, and was transformed to a continuous blood pressure estimate using multipoint nonlinear regression calibration based on the individual subject's sphygmomanometer readings. Bland–Altman limits of agreement between PTT-derived SBP estimates and sphygmomanometer values were –24.7 to 24.1 mmHg, and between Portapres and sphygmomanometer SBP values were –42.0 to 70.1 mmHg. For beat-to-beat SBP estimation during exercise, PTT measurement combined with multipoint nonlinear regression calibration based on intermittent sphygmomanometry may be an alternative to volume clamp devices.

Toward Ubiquitous Blood Pressure Monitoring via Pulse Transit Time: Theory and Practice.

Ubiquitous blood pressure (BP) monitoring is needed to improve hypertension detection and control and is becoming feasible due to recent technological advances such as in wearable sensing. Pulse transit time (PTT) represents a well-known potential approach for ubiquitous BP monitoring. The goal of this review is to facilitate the achievement of reliable ubiquitous BP monitoring via PTT. We explain the conventional BP measurement methods and their limitations; present models to summarize the theory of the PTT-BP relationship; outline the approach while pinpointing the key challenges; overview the previous work toward putting the theory to practice; make suggestions for best practice and future research; and discuss realistic expectations for the approach.

3D.09

Objective: Increased blood pressure (BP) variability is a possible independent risk factor for cardiovascular events. BP variability has been assessed with several methods of BP measurement in recent literature, although it is unclear whether these measurements of variability with varying timeframes reflect the same phenomenon. The aim of our study was to compare the agreement between ambulatory, home and office BP variability. Design and method: The study population consisted of 509 participants randomly drawn from the population register or recruited by general practitioners on the basis of newly diagnosed untreated hypertension. Ambulatory 24-h blood pressure monitoring, 28 home BP measurements (twice every morning and evening during 7 consecutive days) and 8 office BP measurements (duplicate measurements on 4 visits) were performed in all participants. 3 log-transformed variability indices (SD, standard deviation; CV, coefficient of variation and ARV, average real variability) were calculated for all measurement methods and Pearson's correlations between them were calculated. The agreement of different methods on the diagnoses of extreme BP variability (participants with variability above the highest decile) was also assessed with kappa coefficients. Results: Systolic/diastolic BP variability was greater in 24-h ambulatory (CV: 12.6 ± 2.8 /15.1 ± 3.4) than home (CV: 4.4 ± 1.8/4.7 ± 2.0, p < 0.001 versus ambulatory CV for both) and office (CV: 4.8 ± 2.6/5.3 ± 2.6, p < 0.001 versus ambulatory CV for both) measurements. Ambulatory daytime variability was greater than night-time variability (CV: 11.0 ± 2.8/13.1 ± 3.5 vs. 9.5 ± 3.8/12.8 ± 4.6, p < = 0.001 for both). Pearson's correlation coefficients for systolic/diastolic variability indices between different measurement methods were 0.08–0.34/0.03–0.26, indicating only negligible to weak positive relationship (Table). The agreement of ambulatory, home and office BP variability measures on diagnoses of extreme systolic/diastolic BP variability was only slight, with the kappa coefficients varying between 0.00–0.20/0.03–0.16. Extreme variability was diagnosed in only two persons with all three methods.Conclusions: Shorter-term and longer-term BP variability assessed with different methods of BP measurement seem to correlate only weakly with each other. Our study suggests that BP variability assessed by different methods and timeframes reflects various phenomena, not a single entity.

PP.09.05

Objective: Subclinical hypothyroidism is associated with an increased risk of cardiovascular morbidity and mortality among older adults. The cardio-ankle vascular index (CAVI) is a sensitive non-invasive marker of arterial stiffness and atherosclerosis. Objective of our prospective study was to assess the impact of thyroid hormone replacement therapy with low doses of L-thyroxine (6.25–25 μg/day) on CAVI index in patients with subclinical hypothyroidism. Design and method: The study involved 232 patients with subclinical hypothyroidism (73 males, 159 females, mean age 52.34 ± 3.67 years) and 207 healthy controls (79 males, 128 females, mean age 49.93 ± 4.32 years). CAVI was measured in all participants using the system VaSera® 1500, adopting the oscillometric method for blood pressure measurement. Blood pressure, ECG and phonocardiography were monitored during the measurement. All patients with subclinical hypothyroidism received thyroxine replacement therapy (mean doses 21.75 ± 3.43 μg) during 12 months in order to establish euthyroid state. After this period, all patients from studied group underwent CAVI measurement. Results: CAVI was significantly higher in patients with hypothyroidism (8.75, 95% CI 6.13–10.52) than in controls (7.03, 95% CI 5.73–9.03; p < 0.01). After 12 months of L-thyroxine substitution, patients with subclinical hypothyroidism had significantly lower CAVI than at baseline (8.75, 95% CI 6.13–10.52 vs 7.10, 95% CI 6.05–9.37; p < 0.01). Conclusions: Hormone replacement therapy with low dosed L-thyroxine may improve vascular function in patients with subclinical hypothyroidism. Patients with cardiovascular risk factors as well as elderly should be closely monitored for the symptoms of iatrogenic hyperthyroidism during the dose titration process.

Preliminary Results for Estimating Pulse Transit Time Using Seismocardiogram1

Preliminary Results for Estimating Pulse Transit Time Using Seismocardiogram1

146 Could Placement of the Blood Pressure Cuff Over the Elbow Rather than the Upper Arm Increase the Accuracy of Automatic Blood Pressure Machines in the Detection of Systolic Blood Pressure?

Automatic blood pressure monitors (oscillometers) with the cuff placed over the upper arm give different systolic BP (SBP) readings to the Korotkoff/Riva-Rocci auscultatory method, influenced by quantity of soft tissue and arm circumference. Other studies have examined whether SBP measurement at the wrist or forearm is more accurate, with limited success. No literature was found on oscillometer use at the elbow. We therefore examined whether oscillometric SBP at the elbow was more accurate than the upper arm and the influence of demographic and anthropometric variables, using simultaneous Doppler return-to-flow at the wrist as the comparative method for SBP. Triplicate SBP readings at the upper arm and elbow were recorded in 62 participants. Bland-Altman plots showed similarly poor agreement between the oscillometers and Dopplers at each cuff position, despite upper arm oscillometry being a clinically validated method of blood pressure measurement. We found a significant difference (p Placing the cuff over the elbow may therefore be a feasible alternative to a cuff over the upper arm, especially in those with a large quantity of non-muscular soft tissue and older people. Additional development of this method and further comparison is needed as we must adapt to the increasingly obese and elderly population.